Method annotation used for methods that should be invoked when the page is first attached to a request. This is
useful for initializations that should occur on each request that involves the page. Often, such initializations will
be balanced by cleanups when the page is detached.

PageAttached methods should take no parameters and return void. They must either have this annotation, or be named
"pageAttached".

To be clear: methods with this annotation (or name) are still invoked even in Tapestry 5.2, which does away with
the page pool.